Plant height was measured from different starting points in an observation. What problem will this create?

Correct answer: Lack of measurement standardisation

The direct answer is A: lack of measurement standardisation. Standardisation means using the same clearly defined procedure each time. For plant height, choose one reference point, such as the soil surface or the base of the stem, keep the plant upright, use the same ruler and units, and measure in the same way. If the starting point changes, one reading may include more or less of the stem than another. The apparent difference may therefore be caused by the measuring method, not real growth. Option A is correct because the observations cannot be compared fairly without a fixed reference point. Option B is wrong because inconsistent measuring does not itself stop plant growth. Option C is wrong because height remains a numerical, quantitative measurement. Option D is wrong because the number of plants or observations does not automatically increase. Memory cue: same object, same starting point, same method, same units.